The barrel of a fountain pen, cylindrical in shape, is `7` cm long and `5` `mm` in diameter. A full barrel of ink in the pin is used up on writing `3300` words on an average. How many words can be written in a bottle of ink containing one-fifth of a litre?

Explanation

Given, length of the barrel of a fountain pen = 7 cm
and daimeter = 5 mm`= (5)/(10) cm = (1)/(c) cm`
`therefore` Radius of the barrel `= (1)/(2 xx2) = 0.25 cm`
Volume of the barrel `= pir^(2)h" "["Since, its shape is cylindrical"]`
`= (22)/(7) xx (0.25)^(2) xx 7`
`22 xx 0.0625 = 1.375 CM^(3)`
Also , given volume of ink in the bottole `= (1)/(5)` of liter `=(1)/(5) xx 1000 cm^(3)= 200 cm^(3)`
Now, `1.375 cm^(3)` ink used for writing number of wards = 3300
`therefore 1 cm^(3)` ink is used for writing number of words `= (3300)/(1.375)`
`therefore 200 cm^(3)` ink used for witing number of words `= (3300)/(1.375) xx 200= 480000`